Do yourself a favor....and this is just my opinion.

If you're thinking about stacks, do a single.

Singles look much better better on smaller trucks than duals. Turnout's look good on dually, but even on a full size single rear truck with a long bed, the turn outs don't look right.

And get a drop in muffler for them. An open stack seems cool at first, but the novelty wears out rear fast when you have it sitting there by your head roaring away as you're going down the highway.